The field of the disclosure relates generally to components having an internal passage defined therein, and more particularly to mold assemblies and methods for forming such components using a lattice structure to position a core that defines the internal passage.
Some components require an internal passage to be defined therein, for example, in order to perform an intended function. For example, but not by way of limitation, some components, such as hot gas path components of gas turbines, are subjected to high temperatures. At least some such components have internal passages defined therein to receive a flow of a cooling fluid, such that the components are better able to withstand the high temperatures. For another example, but not by way of limitation, some components are subjected to friction at an interface with another component. At least some such components have internal passages defined therein to receive a flow of a lubricant to facilitate reducing the friction.
At least some known components having an internal passage defined therein are formed in a mold, with a core of ceramic material extending within the mold cavity at a location selected for the internal passage. After a molten metal alloy is introduced into the mold cavity around the ceramic core and cooled to form the component, the ceramic core is removed, such as by chemical leaching, to form the internal passage. However, at least some known cores are difficult to position precisely with respect to the mold cavity, resulting in a decreased yield rate for formed components. For example, some molds used to form such components are formed by investment casting, in which a material, such as, but not limited to, wax, is used to form a pattern of the component for the investment casting process, and at least some known cores are difficult to position precisely with respect to a cavity of a master die used to form the pattern. Moreover, at least some known ceramic cores are fragile, resulting in cores that are difficult and expensive to produce and handle without damage. For example, at least some known ceramic cores lack sufficient strength to reliably withstand injection of the pattern material to form the pattern, repeated dipping of the pattern to form the mold, and/or introduction of the molten metal alloy.
Moreover, at least some known components have material property requirements for casting and/or operational use that vary locally throughout the component, and the chemistry of the metal alloy used to form the component is selected based on a balance of such local material property requirements. However, the selected alloy chemistry chosen to satisfy a first local material property requirement in a first area of the component potentially diminishes a desired second local material property requirement in a second area of the component.
Alternatively or additionally, at least some known components having an internal passage defined therein are initially formed without the internal passage, and the internal passage is formed in a subsequent process. For example, at least some known internal passages are formed by drilling the passage into the component, such as, but not limited to, using an electrochemical drilling process. However, at least some such drilling processes are relatively time-consuming and expensive. Moreover, at least some such drilling processes cannot produce an internal passage curvature required for certain component designs.